Rename characters
When prompted to enter a new name for Robin, press Select(3). Enter a new name for Robin, and you can now enter a new name for Gerald, Ivan, and Mary. Press Up, Down, Up, Down, Left, Right, Left, Right, Up, Right, Down, Left, Up, Select to enter new names for the other remaining characters.

Dijiin
Make sure you set your Dijiin the way you want before a battle. If you know you are going to fight a lot of enemies, it would be a good idea to have your Dijiin ready to summon. If you are going to fight a small number of enemies you should not have it ready to summon. Use your Dijiin according to the element the person using the Dijiin excels at. Give Earth to Issac, Fire to Garet, Wind to Ivan, and Water to Mia.

Psyenergy
Use your Psyenergy wisely. You should not just use your Psyenergy at any time, because you will quickly run out. You should only use it when needed or when it will stop you from receiving considerable damage.

Herbs
Carry plenty of herbs in dungeons. Even a small task in a dungeon can wipe you out. You will save more money by doing this than by having to revive one of your team members. You will also always have all your team members ready to fight.

Inns
Use the inns whenever needed. Inns are your best and cheapest source to get healed quickly. Use them even for minor damage, or just to recover lost Psyenergy. Inns are inexpensive and efficient.